JP2000199872A - Illumination device and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to reduce space coherence or to decrease speckles in spite of constitution which is compact and may be industrially mass produced. SOLUTION: This illumination device has a first reflection member 14 having plural reflection surfaces with respectively have angles of inclination of approximately 45 deg. with the optical axis of coherent incident light and are disposed to each other apart prescribed intervals in the optical axis direction of the incident light, a second reflection member 15 which respectively have angles of inclination of approximately 45 deg. with the optical axis of the reflected light by the first reflection member 14 and are disposed to each other apart prescribed intervals in the optical axis direction of the incident light and a lens array member 16 having plural lenses which are disposed within the plane approximately perpendicular to the optical axis of the reflected light by this second reflection member 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device and an image display device having the same.

[0002]

2. Description of the Related Art Conventionally, as one form of an image display device, there is an optical projector configured to illuminate a liquid crystal panel for displaying an image and project its reflected light or transmitted light on a screen. In such a projector, a lamp such as a metal halide, halogen, or xenon is generally used as a light source. However, such a lamp light source has some disadvantages as follows, which hinders its usefulness.

[0003] First, lamps have a short life, and even metal halide lamps last for about 2,000 hours. For this reason, it is necessary to devise a configuration such that the cartridge can be exchanged by being housed in a detachable cartridge.

Further, since the three primary colors of light are usually cut out from white light from a lamp, the optical system for that purpose has the drawback that the volume is large, the color reproduction area is limited, and the light use efficiency is also low. descend.

To solve these problems, attempts have been made to use an optical semiconductor device such as a light emitting diode or a semiconductor laser as a light source. For example, the life of a light emitting diode is generally as excellent as 10,000 hours or more. However, a light emitting diode generally has low directivity of light and emits light by diverging. Therefore, it is not easy to improve light use efficiency.

[0006] In this respect, the semiconductor laser can efficiently use light emitted with excellent directivity. In addition, semiconductor lasers also have a sufficiently long life, and generally have higher energy utilization efficiency than light emitting diodes. further,
A semiconductor laser can have a large color reproduction region due to its monochromaticity.

[0007]

However, when a semiconductor laser is used as a light source such as the above-mentioned projector, there is a problem of speckle noise as described below.

In general, when a laser light source is used for illumination of an image display device, for example, on an image plane, for example, on the retina of an observer, contributions from an object plane, for example, points and areas of a screen are gathered to form an image. Can be considered. At this time, since it is natural for the object surface to have irregularities with a depth of about the wavelength or more, light beams having a complicated phase relationship overlap on the image plane, and if the light beams are coherent with each other, Interference results in complex light and dark patterns. This is speckle, and in the case of a display device, it causes a significant deterioration in image quality. Semiconductor lasers also have a problem of coherence sufficient to generate speckle noise in general.

As another method of displaying images using a laser, a laser scanning type configuration is also known, but in this case, speckle noise also becomes a problem. In general, the basic configuration of a laser scanning type image display device is that a light emitted from a laser light source is condensed by a lens, the spot is projected onto a point on a screen, and a condensed spot is deflected by a deflector arranged in an optical path. Is two-dimensionally scanned on a screen to display an image, and a human sees transmitted light or reflected light from the screen.

At this time, on the image plane on the retina, the luminous flux in the condensed spot overlaps at the image point with a random phase change on the screen. In this way, the light path length difference from the light source of the light beams overlapping on the retina is extremely small, and they interfere with each other to generate speckle.

Speckle noise is a common problem not only in semiconductor lasers but also in laser light sources having high coherence, and many attempts have been made to solve them. One of the typical methods is a method using a rotating diffusion plate. This involves inserting a random diffuser such as frosted glass between the illumination light source and the surface to be illuminated, and rotating it to temporally fluctuate the speckle pattern that occurs on the image plane, thereby increasing the response speed of the light receiving system. This is a method of averaging the pattern by the integration effect within the pattern. For example, in the case of the human eye, the response speed is said to be about 30 msec. If the diffuser is rotated at a sufficient speed so that the pattern fluctuates multiple times within that time, the human eye will not be able to reach the specifications. Can be made almost unrecognizable.

However, since the rotating diffusion plate has an action of diverging light by nature, when it is inserted into an optical system, a loss of incident light occurs. In particular, in the case of the laser scanning type, the loss is large with respect to the amount of light that can be collected on the screen after passing through the rotating diffusion plate. Further, a rotating diffusion plate rotated by a motor takes up volume, consumes energy, generates driving noise, and is not preferable as a consumer image display device.

Another method for reducing speckle noise is to divide a coherent light beam having a certain coherence length into a plurality of light fluxes, give an optical path difference larger than the coherence length to each other, and then merge or arrange them again. is there. In this reduction method, non-coherence occurs between the light beams. Therefore, as the number of split light beams increases, the degree of spatial coherence of the combined or arranged coherent light can be reduced. As a specific known configuration, a fiber bundle is known. In this method, multiple fibers are bundled and the length of each fiber is
An optical path difference longer than the coherence length of the incident light source is given. When both ends of the fiber are aligned and light enters from one end, the light emitted from each fiber becomes non-coherent at the other end, and the spatial coherence as a whole is reduced. Therefore, when this is used as a light source such as illumination, the speckle on the surface to be irradiated can be reduced.

However, the method using the fiber bundle has the following problems. For example, when 51 optical fibers are bundled and the difference in length between them is 1 cm, the difference in length between the shortest optical fiber and the longest optical fiber is 50 cm. Then, a very large volume is required to align both ends thereof, for example, to be accommodated in an image display device, which is an obstacle to downsizing the image display device. Also, the aperture ratio at the input end of the fiber bundle is 1
Because of the following, a loss occurs when the incident coherent light is coupled into the fiber bundle. Further, at the output end, a light beam is output from each fiber, that is, the output light is composed of a light beam diverging from each point of the output port having a wide area, which causes a loss in a subsequent optical system. Also. Furthermore, it is basically difficult to mass-produce devices such as fiber bundles, which is also unsuitable for consumer image display devices.

By the way, no matter what optical path length difference is used, the coherence length of the coherent light emitted from the coherent light source having a single mode power spectrum is generally sufficiently long, so that the spatial coherence is reduced. There are limits to doing so. For example,
When a single-mode semiconductor laser is used as a light source, its typical spectrum width is 100 MHz, and the coherence length is about 3 m. An optical system that generates such a long optical path difference requires a considerable volume, and is a major hindrance when used in a consumer image display device.

Accordingly, the present invention has been proposed in view of the above-mentioned circumstances, and has a compact structure capable of industrially mass-producing, while reducing spatial coherence or speckle. It is an object of the present invention to provide a device and an image display device provided with the device.

[0017]

In order to solve the above-mentioned problems, an illumination apparatus according to the present invention has an inclination angle of approximately 45 degrees with respect to the optical axis of a coherent incident light, and has a tilt angle of approximately 45 degrees. A first reflecting member having a plurality of reflecting surfaces disposed at predetermined intervals in an optical axis direction of the first reflecting member;
A second reflecting member having a plurality of reflecting surfaces having a tilt angle of degrees and being arranged at predetermined intervals in the optical axis direction of the incident light, and light reflected by the second reflecting member; A lens array member having a plurality of lenses disposed in a plane substantially perpendicular to the axis and a condenser lens are provided.

In this lighting device, the incident light is reflected by the first and second reflecting members sequentially,
The luminous flux of the incident light is divided into a plurality of luminous fluxes having a predetermined optical path length difference, and each of the plurality of luminous fluxes is incident on each lens of the lens array member substantially in a one-to-one manner, and is passed through a condenser lens. To illuminate the same area of the surface to be illuminated.

Further, in the illumination device according to the present invention, each of the illumination devices has an inclination angle of approximately 45 degrees with respect to the optical axis of the coherent incident light and is separated from each other by a predetermined distance in the optical axis direction of the incident light. A first reflecting portion having a plurality of reflecting surfaces disposed thereon, and an optical axis of the incident light which has an inclination angle of approximately 45 degrees with respect to an optical axis of light reflected by the first reflecting portion; A second reflector having a plurality of reflective surfaces disposed at predetermined intervals in the direction, and disposed in a plane substantially perpendicular to the optical axis of light reflected by the second reflector; An optical element integrally formed with a lens array section having a plurality of lenses and a condenser lens are provided.

The illumination device divides the luminous flux of the incident light into a plurality of luminous fluxes having a predetermined optical path length difference by sequentially reflecting the incident light of the optical element at the first and second reflecting portions. And each of these multiple light fluxes
The light is incident on each lens of the lens array section substantially in one-to-one correspondence, and the same area of the irradiated surface is illuminated via a condenser lens.

Further, an image display device according to the present invention includes the above-mentioned illumination device and an image display unit for displaying an image illuminated by the illumination device.

In the above-described means, the incident coherent light is two-dimensionally divided in a plane perpendicular to the optical axis, and becomes a plurality of light beams having optical path differences. Each light beam is two-dimensionally arranged at a predetermined interval, and is emitted through one of the lenses constituting the lens array. The plurality of emitted light beams have substantially the same focal position, and reach a surface to be illuminated by a condensing lens disposed at a subsequent stage. At that time, the irradiated surface is disposed at the rear focal position of the condenser lens, that is, each divided light beam irradiates substantially the same region on the focal plane. Therefore, the light flux reaching one point in the irradiated area is constituted by a superposition of a plurality of light fluxes having optical path differences, and is made incoherent with each other by appropriately selecting the optical path difference. Speckle on the irradiation surface can be reduced.

When the lighting device according to the present invention is used for an image display device, it is possible to obtain a high-quality image by reducing speckles.

When the incident coherent light has a plurality of different wavelengths, for example, when a multi-mode semiconductor laser is used as a light source, the following operation can be obtained. As described in detail in Japanese Patent Application No. 10-137823, a multi-mode laser generally has a plurality of oscillation frequencies at regular intervals determined by the laser cavity length of the laser, and a coherence degree obtained from a power spectrum is also high.
Indicates the maximum of one run interval. The full width at half maximum of the maximum waveform is τ _t
And the distance between the maximum waveform and the adjacent maximum waveform is τ
when the _d, the optical path difference l of a 2 light fluxes, c {(n-1) τ d + τ t / 2} <l <c (nτ d -τ t /
If 2) is satisfied, the two light beams are regarded as substantially incoherent, and hardly interfere with each other. Where c
Is the speed of light and n is a natural number. For example, in the case of a multimode semiconductor laser, cτ _d ≒ 0.5 mm and cτ _t ≒ 4.0 m
m. Therefore, in this case, between the two beams
For example, if an optical path length difference of 3 mm is generated, it is possible to effectively reduce speckle by applying to the above-described lighting device.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can be applied to an illuminating device that handles coherent light emitted from a light source that emits coherent light, such as a semiconductor laser, and an image display device having the same.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1] As shown in FIG. 1, a lighting device according to the present invention comprises a first step mirror 14 as a first reflecting member and a second reflecting member constituting an optical element 13. Second step mirror 15 and lens array 1
6.

This illumination device has a semiconductor laser light source unit 11 and a reflection mirror 12. The semiconductor laser light source unit 11 is composed of a semiconductor laser and an optical component for shaping a beam of emitted light or a collimating lens, and emits a substantially circularly collimated light beam.

As shown in FIG. 2, the semiconductor laser oscillates at a plurality of periodic oscillation frequencies, that is, a so-called multi-mode, and its coherence degree also periodically shows a local maximum as shown in FIG. Let the full width at half maximum of the first maximum waveform be l
and _t, the maximal value distance between the second local maximum waveform adjacent to the first local maximum waveform and the first maximum waveform and l _d, for example, l _t ≒ 0.2mm, a l _d ≒ 4 mm.

The light emitted from the semiconductor laser light source unit 11 is
The optical axis is bent by 45 ° by the reflection mirror 12, and + x
In the direction, and enters the optical element 13. The schematic configuration of the optical element 13 will be described below with reference to FIGS. The incident light beam first reaches a first step mirror 14 which is a first reflection member constituting the optical element 13. As shown in FIG. 4, the first step mirror 14 is configured such that a plurality of reflection mirrors 42 inclined at 45 ° with respect to the incident surface 41 are arranged in parallel at intervals of d _s1 . Therefore, when the optical axis of the incident light beam is bent by 45 ° in the + y direction by the first snub mirror 14 and viewed in a plane perpendicular to the y axis,
The light is divided into strip-shaped light beams arranged at intervals of _ds1 . Also, between each adjacent light flux, when viewed from the light source,
An optical path difference of d _s1 is generated.

Thereafter, the split light beam enters a second step mirror 15 as a second reflecting member. As shown in FIG. 5, the second step mirror 15 is configured such that a plurality of reflection mirrors 52 inclined at 45 ° with respect to the incident surface 51 are arranged in parallel at intervals of d _s2 . Therefore, the incident light divided into strips has its optical axis bent by 45 ° in the + z direction by the second step mirror 15 and, when viewed in an xy plane perpendicular to the z axis, d is applied in the x direction. _s1 interval, d in y direction
The light is split into lattice-like light beams arranged at intervals of _s2 .

Further, an optical path difference is generated between the light beams in units of d _s1 and d _s2 . A lens array 16 is further provided in the xy plane. As shown in FIG. 6, the lens array 16 includes a plurality of lenses periodically arranged at intervals of d _{s1 in} the x direction and d _{s2 in the} y direction. First snub mirror 14
And the luminous flux split by the second step mirror 15
Each of them enters and transmits one of the lenses in the lens array 16 in a one-to-one correspondence.

The light beam transmitted through each lens of the lens array 16 illuminates the same area of the irradiated surface arranged at the focal position of the condenser lens via the condenser lens.

As a result, an optical path difference having a unit of d _s1 and d _s2 is generated between a plurality of light fluxes transmitted through the lens array 16, and (m−1) l _d +1 for d _s1 and d _s2. When _{t / 2 ≦ d s1 ≦ ml} d -l t / 2 (m-1) l d + l t / 2 ≦ d s2 ≦ ml d -l t / 2, can be mutually incoherent to each beam . Here, m is a natural number.

[Embodiment 2] Further, as shown in FIG. 7, a lighting device according to the present invention has a
4. Second step mirror unit 75 and lens array unit 76
May be configured as a single transparent optical element.

The semiconductor laser light source unit 71 is the same as the semiconductor laser light source unit 11 shown in FIG. 1, and emits the multi-mode coherent light by collimating the light and makes the light enter the optical element 73 via the reflection mirror 72. .

The optical element 73 includes a first step mirror unit 7
4. Second step mirror unit 75 and lens array unit 7
A single transparent prism-like optical element having 6;
It may be manufactured integrally, or may be a unit having components having the respective parts and bonded together with matching refractive indexes. The optical element 73 has an outer surface portion having the same shape as the reflection surface of the above-described step mirror, and basically has the same operation as the optical element 13 shown in FIG. That is, a plurality of split light beams are emitted from the lens array unit 76. However, assuming that the refractive index of the material constituting the optical element 73 is uniform and n between the light beams, nd _s1 and n _ds1
An optical path difference is generated in units of d _s2 . For nd _s1 and _{nd s2, (m-1)} l d + l t / 2 ≦ nd s1 ≦ ml d -l t / 2 (m-1) l d + l t / 2 ≦ nd s2 ≦ ml d -l t / Assuming that 2, the light beams can be made incoherent with each other.

Also in this optical element, the light beam transmitted through each lens of the lens array section 76 illuminates the same area of the illuminated surface located at the focal position of the condenser lens via the condenser lens. .

If the optical element is integrated into a single component as in the present embodiment, mass production can be achieved at low cost, such as injection molding using a mold, which is industrially advantageous.
At this time, it is important that the transparent optical element 73 has a high transmittance with respect to the wavelength of the incident light, but in addition to optical glass such as silica glass, an organic material such as polycarbonate resin or polymethyl methacrylate resin is used. Can be used.

Further, since these optical materials generally have a refractive index n larger than 1, the optical material has the same size as that shown in FIG. If so, the optical path length difference can be made larger. Conversely, the size of the entire apparatus can be reduced.

Further, in this optical element, the transparent optical element 73 may be integrated with a reflection mirror 72, an optical part for beam forming or collimating the light emitted from the semiconductor laser in the semiconductor laser light source 71, and the like. Can,
Further, the number of parts can be reduced.

[Embodiment 3] Further, the illumination device according to the present invention can constitute an image display device as shown in FIG.

The light beam emitted from the lens array of the illuminating device 81 having the above-described configuration is condensed for each element lens, and reaches the condenser lens 82. An irradiated surface 83 is arranged on a rear focal plane of the condenser lens 82.

Therefore, the light beam emitted from each lens array irradiates substantially the same area on the surface to be irradiated. Conversely, the light flux reaching one point on the irradiated surface 83 is
The light path difference generated in the illuminating device 81 constitutes a superposition of light beams that are incoherent with each other, and speckles on the irradiated surface 83 can be reduced.

As is apparent from FIG. 6, the illumination device 81 divides the incident light beam of the coherent light source in a plane perpendicular to the optical axis. The intensity distribution on the surface is averaged and made uniform. Further, the illuminated area is generally rectangular, and its aspect ratio can be determined by appropriately selecting the mirror length of the first step mirror (portion) and the mirror length of the second step mirror (portion) of the illumination device 81. Can be arbitrarily designed. That is, when the first step mirror and the second step mirror similar to the optical elements shown in FIGS. 1, 4 and 5 are used for the illumination device 81, by appropriately selecting d _m1 and d _m2 , The aspect ratio of the illumination area can be arbitrarily designed.

In order to constitute an image display device provided with the illumination device according to the present invention, for example, a spatial light modulator of liquid crystal is arranged on the surface to be irradiated 83 shown in FIG. A configuration in which an image is displayed by projecting light onto a screen by a projection lens may be employed.

In the above embodiment, a multi-mode semiconductor laser oscillating at a plurality of frequencies is used as a light source. However, a multi-mode semiconductor laser may have a plurality of oscillation wavelengths. It can also be obtained by adding a high-frequency signal to an injection current of a semiconductor laser oscillating at a single wavelength. The semiconductor laser of such a multi-mode, generally l _t is small, the configuration for obtaining the effect of speckle reduction described above is relatively easy. However, the coherent light source is not limited to a multi-mode semiconductor laser, but can be generally applied to a laser light source that is a coherent light source by using the same principle.

[0048]

As described above, according to the illumination device and the image display device according to the present invention, the incident light is divided into a plurality of light beams and the light path is reduced while having a configuration that is small and can be mass-produced at low cost. Since a length difference is generated, the spatial coherence of the emission light surface can be effectively reduced.

If a multimode laser having a plurality of different oscillation wavelengths is used as the light source, the optical path length difference can be optimized using the periodic coherence degree, and the spatial coherence can be effectively reduced. Can be achieved.

According to the illuminating device of the present invention, the incident light is divided into a plurality of light beams, an optical path length difference is generated, and each light beam is emitted through a lens. It is possible to provide uniform illumination with reduced crackling. Therefore, in the image display device equipped with this illumination device, it is possible to provide a small-sized, high-quality image with reduced speckle noise with a small number of components, without the need for high-precision positioning or the like. Becomes

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a lighting device according to the present invention.

FIG. 2 is a graph showing an oscillation frequency of a semiconductor laser.

FIG. 3 is a graph showing the degree of coherence of a semiconductor laser.

FIG. 4 is a perspective view showing a shape of a first reflecting member constituting the lighting device.

FIG. 5 is a perspective view showing a shape of a second reflection member constituting the lighting device.

FIG. 6 is a plan view showing a shape of a lens array member constituting the lighting device.

FIG. 7 is a perspective view showing another embodiment of the configuration of the lighting device according to the present invention.

FIG. 8 is a perspective view showing a configuration of an image display device according to the present invention.

[Explanation of symbols]

Reference Signs List 11 semiconductor laser light source unit, 14 first step mirror, 15 second step mirror, 16 lens array

Claims (7)

[Claims] 1. A plurality of reflecting surfaces each having an inclination angle of approximately 45 degrees with respect to an optical axis of a coherent incident light and arranged at a predetermined distance from each other in an optical axis direction of the incident light. A first reflecting member having a tilt angle of approximately 45 degrees with respect to the optical axis of the light reflected by the first reflecting member, and a predetermined interval in the optical axis direction of the incident light. A second reflecting member having a plurality of reflecting surfaces disposed in the same direction, and a plurality of lenses disposed in a plane substantially perpendicular to an optical axis of light reflected by the second reflecting member. An array member and a condensing lens, and by sequentially reflecting the incident light on the first and second reflecting members, divides the light beam of the incident light into a plurality of light beams having a predetermined optical path length difference, Each of the plurality of light beams is substantially applied to each lens of the lens array member. The light beams transmitted through these lenses are made to correspond to each other one by one, and the light beams transmitted through these lenses are transmitted through the above-mentioned condensing lens to illuminate the same region of the irradiated surface arranged at the focal position of this condensing lens. Lighting device characterized by the following. 2. The illumination device according to claim 1, wherein an optical path length difference between a plurality of light beams split from the incident light is longer than a coherence length of the incident light. 3. A light source for emitting coherent incident light to be incident on the first reflecting member, wherein the incident light has a plurality of different periodic oscillation wavelengths, and represents a degree of coherence of the incident light as a function of time. , The full width at half maximum of the first maximum waveform is τ _1, and the first maximum waveform is
The distance between the local maximum values of the local maximum waveform and an adjacent second local maximum waveform is set to τ _d, and a plurality of reflecting surfaces constituting the first reflecting member are arranged at a constant interval d ₁ . When a plurality of reflecting surfaces constituting the reflecting member are arranged at a fixed interval d ₂ , for d ₁ and d ₂ , c ((n−1) τ _d + τ _t / 2) ≦ d ₁ ≦ c ( nτ _d −τ _t
/ 2) c ((n−1) τ _d + τ _t / 2) ≦ d ₂ ≦ c (nτ _d −τ _t
/ 2) (where c is the speed of light and n is a natural number). 4. A plurality of reflecting surfaces each having an inclination angle of approximately 45 degrees with respect to the optical axis of the coherent incident light and arranged at a predetermined distance from each other in the optical axis direction of the incident light. And a first reflecting portion having an inclination angle of approximately 45 degrees with respect to the optical axis of the light reflected by the first reflecting portion and spaced apart from each other by a predetermined distance in the optical axis direction of the incident light. A second reflector having a plurality of reflection surfaces disposed in the same direction, and a plurality of lenses disposed in a plane substantially perpendicular to an optical axis of light reflected by the second reflector. An optical element integrally formed with an array portion; and a condenser lens, wherein the incident light is reflected by the first and second reflecting portions of the optical element in sequence. Is divided into a plurality of light beams having a predetermined optical path length difference from each other, and each of the plurality of light beams is Are incident on each lens of the lens array section substantially in a one-to-one correspondence, and the light beam transmitted through each lens is transmitted through the condensing lens, thereby forming a light-receiving element disposed at the focal position of the condensing lens. An illumination device for illuminating the same area on an irradiation surface. 5. The lighting device according to claim 4, wherein an optical path length difference between a plurality of light beams split from the incident light is longer than a coherence length of the incident light. 6. A light source which emits coherent incident light to be incident on the first reflecting portion, wherein the incident light has a plurality of different periodic oscillation wavelengths, and represents a degree of coherence of the incident light as a function of time. , The full width at half maximum of the first maximum waveform is τ _1, and the first maximum waveform is
The distance between the local maximum values of the maximum waveform and the adjacent second maximum waveform is defined as τ _d, and a plurality of reflection surfaces constituting the first reflection unit are arranged at a constant interval d ₁ . when multiple reflecting surfaces constituting the reflective portion is disposed at a predetermined interval d _2, for d ₁ and _{d 2, c ((n-} 1) τ d + τ t / 2) ≦ d 1 ≦ c ( nτ _d −τ _t
/ 2) c ((n−1) τ _d + τ _t / 2) ≦ d ₂ ≦ c (nτ _d −τ _t
/ 2) (where c is the speed of light and n is a natural number). 7. A plurality of coherent incident lights emitted from a light source, each of which has an inclination angle of approximately 45 degrees with respect to the optical axis of the coherent incident lights and are arranged at a predetermined interval from each other in the optical axis direction of the incident lights. A first reflecting member having a reflecting surface, and an inclined angle of approximately 45 degrees with respect to the optical axis of the light reflected by the first reflecting member. A second reflecting member having a plurality of reflecting surfaces disposed at intervals, and a plurality of lenses disposed in a plane substantially perpendicular to an optical axis of light reflected by the second reflecting member; And a condensing lens, and the incident light is reflected by the first and second reflecting members sequentially to divide the light of the incident light into a plurality of light having a predetermined optical path length difference from each other. Each of the plurality of light beams is substantially applied to each lens of the lens array member. An illuminating unit that irradiates the same area of the irradiated surface arranged at the focal position of the condenser lens by transmitting the light flux transmitted through each of the lenses through the condenser lens by causing the light beams to be incident in one-to-one correspondence with each other. An image display device comprising: an image display unit configured to display an image, wherein the image display unit is illuminated by the illumination unit.